The 'Dark Knight' actor - who is no stranger to transforming his physical shape for a part - has revealed he didn't look at "numbers" to prepare for the role of Dicky Eklund, a former welterweight boxer who was also a drug-addict in 'The Fighter' and needed make-up at times to help him look skinnier.

The 36 year old said: "I'm a good 60 pounds heavier than a welterweight. I can't lose that much weight, because I wouldn't be able to box and train and everything. I didn't look at numbers, I didn't look at scale, I just went down to what looked like might be the right body type for Dicky and the way that he fights as well."

"I couldn't go too far because if I went too far, I'd be able to play the crackhead side, but then after jail, he got clean mentally and physically, and he's always wiry, he's always lean, but I had to be able to show that. So we needed make-up to help me out a great deal with that."

Christian famously ate just a can of tuna and an apple a day in 2004 to drops 60lbs for his role in 'The Machinist'.

Last year he also admitted to considering using steroids to bulk up when he was starring in 'American Psycho' and 'Batman Begins'.

However, he promises that he doesn't deliberately choose films that challenge him physically.

He told MTV News: "I have no goal of seeing if I can become invisible one day, eat so little that I disappear.

"I didn't take this job because I went, 'Oh, there's a physical transformation needed.' I always go, 'Damn! There's a physical transformation needed!'

"Again, I just didn't recognize that. I just liked the character and then realized, 'Oh, c**p, he's a welterweight.' "